An overwhelming number of vehicle thefts involve penetration into the passenger compartment of the vehicle. Systems are available generally that when armed, detect the opening of vehicle doors, hood or trunklid, such as by monitoring switches actuated upon such opening occurrences. Systems are also generally available that when armed, detect bumping or jarring of the vehicle, such as may be incidental to forced penetration into the vehicle. However, these systems do not detect all forms of penetration into the passenger compartment, such as those not accompanied by the opening of doors or by bumping or jarring of the vehicle. A system has been proposed in U.S. Pat. No. 4,638,294 to detect intrusion by propagating an electromagnetic wave through the vehicle interior and monitoring the amplitude of the received wave which may change upon intrusion into the vehicle. However, such a system requires additional expense of adding sophisticated electromagnetic transmitting and receiving means into the vehicle. Accordingly, what is needed is a comprehensive vehicle intrusion detection system that may be provided at minimal cost.